Showing papers by "Barbara A. Gower published in 2014"

Insulin Resistance Indices Are Inversely Associated With Vitamin D Binding Protein Concentrations

Abstract: Context: We hypothesized that, similar to the coordinated homeostatic regulation of most hormones, the concentration of free and bioavailable 25-hydroxyvitamin D [25(OH)D] will be tightly controlled by total 25(OH)D and vitamin D binding protein (VDBP) and that the VDBP concentrations will be associated with insulin resistance status. Objective: Our primary objective was to investigate associations between total, free, and bioavailable 25(OH)D and VDBP. We also evaluated the relationships of VDBP with insulin resistance indices. Study Design: The study design was cross-sectional in the setting of a university children's hospital. The relative concentration of bioavailable 25(OH)D to total 25(OH)D [bioavailable 25(OH)D/total 25(OH)D was expressed as a percentage [percentage bioavailable 25(OH)D]. Results: Subjects were 47, postmenarchal, female adolescents, with a mean age of 15.8 ± 1.4 years, a mean body mass index of 23.1 ± 4.0 kg/m2. The total 25(OH)D was strongly associated with VDBP (rho = 0.57, P < ....

Effects of a eucaloric reduced-carbohydrate diet on body composition and fat distribution in women with PCOS☆

Abstract: Objective To determine if consumption of a reduced-carbohydrate (CHO) diet would result in preferential loss of adipose tissue under eucaloric conditions, and whether changes in adiposity were associated with changes in postprandial insulin concentration.

Associations between vascular health indices and serum total, free and bioavailable 25-hydroxyvitamin D in adolescents.

Abstract: Objective The role of vitamin D in cardiovascular health remains debated as results have been inconsistent. Previous studies have not considered the bioavailability of 25-hydroxy vitamin D [25(OH)D]. Objectives of our study were to investigate the association between serum concentrations of total, free and bioavailable 25(OH)D and independent predictors of cardiovascular risk such as flow mediated dilatation (FMD) and augmentation index (AIx). Design This cross-sectional study included 47 post-menarchal, adolescent females [31 African American (AA) and 16 European American (EA)]. Methods AIx was standardized to a heart rate of 75 beats/min (AIx75). Free and bioavailable 25(OH)D concentrations were calculated from standard formulas. Results and Conclusions Mean age of the participants was 15.8±1.4 years and mean body mass index was 23.1±4.0 kg/m2. Serum total 25(OH)D was not associated with FMD, but was positively associated with AIx75 in the adjusted model (rho = 0.4, P = 0.03). AIx75 was positively associated with bioavailable 25(OH)D (rho = 0.4, P = 0.004) and free 25(OH)D (rho = 0.4, P = 0.009) and the associations persisted after adjusting for covariates. In race-specific analyses, total, free and bioavailable 25(OH)D were strongly positively associated with AIx75 in AA (rho = 0.5, 0.4, 0.4, respectively), which persisted even after adjusting for covariates. Whereas in EA there was an inverse association between total 25(OH)D and AIx75 in EA (rho = −0.6), which attenuated after adjusting for covariates. Conclusion Circulating total, free and bioavailable 25(OH)D were associated with arterial stiffness in adolescent girls, and these associations were race dependent. Notwithstanding, the implications of associations between vascular function indices and 25(OH)D remains unclear.

Cardiorespiratory fitness in older adult women: relationships with serum 25-hydroxyvitamin D

Abstract: Previous studies suggest that circulating 25(OH)D may favorably influence cardiorespiratory fitness and fat oxidation. However, these relationships have not been examined in older adult women of different ethnic groups. The objectives of this study were to determine whether serum 25(OH)D is related to cardiovascular fitness (VO2max) in sedentary women ages ≥60 years and to determine whether these associations differ between African Americans (AA) and European Americans (EA). A secondary aim was to determine whether serum 25(OH)D is correlated with respiratory quotient (RQ) during submaximal exercise. This cross-sectional analysis included 67 AA and EA women ages 60–74 years. VO2max was measured by a modified Bruce graded treadmill protocol, and measurements were adjusted for percent fat and lean body mass assessed by air displacement plethysmography. Indirect calorimetry was used to measure RQ at rest and during four submaximal exercise tests. Fasting blood samples were obtained to quantify serum 25(OH)D. Serum 25(OH)D was associated with VO2max (ml/kg LBM/min) independent of percent body fat (r = 0.316, p = 0.010). However, subgroup analysis revealed that this relationship was specific to AA (r = 0.727, p = 0.005 for AA; r = 0.064, p = 0.643 for EA). In all subjects combined, 25(OH)D was inversely correlated (p < 0.01) with all measures of submaximal RQ. Higher serum 25(OH)D was associated with greater cardiorespiratory fitness in older adult AA women. Among both AA and EA, inverse associations between serum 25(OH)D and RQ suggest that women with higher levels of circulating vitamin D also demonstrated greater fat oxidation during submaximal exercise.

Calorie restriction in overweight seniors: response of older adults to a dieting study: the CROSSROADS randomized controlled clinical trial.

Abstract: We conducted a study designed to evaluate whether the benefits of intentional weight loss exceed the potential risks in a group of community-dwelling obese older adults who were at increased risk for cardiometabolic disease. The CROSSROADS trial used a prospective randomized controlled design to compare the effects of changes in diet composition alone or combined with weight loss with an exercise only control intervention on body composition and adipose tissue deposition (Specific Aim #1: To compare the effects of changes in diet composition alone or combined with weight loss with an exercise only control intervention on body composition, namely visceral adipose tissue), cardiometabolic disease risk (Specific Aim #2: To compare the effects of a change in diet composition alone or combined with weight loss with an exercise only control intervention on cardiometabolic disease risk), and functional status and quality of life (Specific Aim #3: To compare the effects of a change in diet composition alone or combined with weight loss with an exercise only control intervention on functional status and quality of life). Participants were randomly assigned to one of three groups: Exercise Only (Control) Intervention, Exercise + Diet Quality + Weight Maintenance Intervention, or Exercise + Diet Quality + Weight Loss Intervention. CROSSROADS utilized a lifestyle intervention approach consisting of exercise, dietary, and behavioral components. The development and implementation of the CROSSROADS protocol, including a description of the methodology, detailing specific elements of the lifestyle intervention, assurances of treatment fidelity, and participant retention; outcome measures and adverse event monitoring; as well as unique data management features of the trial results, are presented in this article.

Exercise dose and diabetes risk in overweight and obese children: A randomized control trial

Abstract: Exercise has been prescribed for diabetes treatment since at least 600 B.C. The early East Indian text, the Shushruta, described a reduction in the sweetness of urine from diabetic patients after exercise. One might think that very little could be left to discover in the field of exercise and diabetes, yet surprisingly this is far from the truth. Ongoing research is refining the exercise prescription for patients of all ages, with the main types of diabetes (gestational, type 1, and type 2) and discovering new ways in which exercise has benefits. Alterations in metabolism caused by diabetes and new types of exercise modalities are also actively being researched. A search of several hundred articles on exercise published between July 1, 2012, to June 30, 2013, uncovered the following 9 articles we felt had the most relevance to patients with diabetes or prediabetes.

Gut hormone activity of children born to women with and without gestational diabetes.

Abstract: Children exposed to gestational diabetes mellitus (GDM) in utero have greater risk for obesity and comorbid health problems as compared to children from non-diabetic mothers (1-3). This effect is believed to be at least partially attributable to altered intrauterine programming of metabolism and body weight regulation. Gut hormones play an important role in the regulation of body weight homeostasis via signaling of hunger and satiety. To date, however, there are no published studies that have examined the concentrations and activity of gut hormones among offspring of women with gestational diabetes (OGD) versus those from a non-diabetic intrauterine environment (CTRL). Ghrelin is a hormone secreted in the stomach and to date, is the only peripheral signal that is known to stimulate food intake (4). Secretion of ghrelin increases prior to a meal and is suppressed following a meal (5). Among obese adults, fasting concentrations of ghrelin tend to be lower, and the post-prandial suppression of ghrelin is blunted (6; 7). Although it appears paradoxical for obese individuals to have lower fasting ghrelin, it has been hypothesized that this pattern is consequent to increased insulin, which is inversely associated with ghrelin, or is an adaptive response to positive energy balance in obese adults (6). Despite consistent findings in studies of adults, studies of lean versus obese children, have yielded less consistent results (8; 9). Glucagon-like peptide 1 (GLP-1) and peptide-tyrosine-tyrosine (PYY) are anorectic hormones that are secreted from L-cells in the ileum of the small intestine in response to feeding. Circulating concentrations of GLP-1 tend to be lower among obese adults and children (10; 11), and the acute increase in GLP-1 following meal consumption may be suppressed in obese states (12). There are two endogenous forms of PYY: 1-36 and 3-36; the latter of these has been more strongly implicated in feeding. Some, but not all (9), studies have shown lower fasting concentrations of PYY3-36 among obese individuals (13; 14). Furthermore, obesity has been consistently associated with suppression of the usual increase in PYY3-36 concentration that occurs following a meal (9; 13; 14). Previous research has not examined whether the response of GLP-1 and PYY to a meal challenge is perturbed among children of women with GDM. The main objective of this study was to compare fasting and postprandial concentrations of ghrelin, GLP-1 and PYY3-36 among children with and without intrauterine exposure to maternal GDM. The secondary objective was to examine whether associations of these hormones with children’s usual food intake differed by group. Differences in body composition, energy intake, physical activity, insulin sensitivity and secretion among OGD versus CTRL from this cohort have been reported previously (2). We hypothesized that, similar to obese individuals, OGD would have lower fasting concentrations of ghrelin, GLP-1, and PYY3-36, and an attenuated postprandial response of these gut hormones. These hypotheses were tested among 5-10 year-old children with and without intrauterine exposure to GDM.

Use of a simple liquid meal test to evaluate insulin sensitivity and beta-cell function in children.

Abstract: Insulin sensitivity and β-cell function are useful indices of metabolic disease risk but are difficult to assess in young children because of the invasive nature of commonly-used methodology. A meal-based method for assessing insulin sensitivity and β-cell function may at least partially alleviate concerns. Objectives of this study were to: 1) determine the association of insulin sensitivity assessed by liquid meal test with that determined by an insulin-modified frequently sampled intravenous glucose tolerance test (FSIGT); 2) examine the association of insulin sensitivity derived from each test with measures of body composition, fat distribution, and metabolic health (lipids, fasting insulin and glucose, and surrogate indices of insulin sensitivity); and 3) examine the associations of indices of β-cell function derived from each test with total and regional adiposity. Forty-seven children (7–12 yr) underwent both a liquid meal test and an FSIGT. The insulin sensitivity index derived from the meal test (SI-meal) was positively associated with that from the FSIGT (SI-FSIGT; r=0.63; P<0.001), and inversely with all measures of insulin secretion derived from the meal test. Both SI-meal and SI-FSIGT were associated with measures of total and regional adiposity. SI-meal, but not SI-FSIGT, was associated with triglycerides and fasting insulin, after adjusting for ethnicity, gender, pubertal stage, and fat mass. Basal insulin secretion measured during the meal test was positively associated with all measures of adiposity, independent of insulin sensitivity. In conclusion, a liquid meal offers a valid and sensitive means of assessing insulin sensitivity and β-cell responsivity in young children.